Vapor space corrosion inhibitor



United States Patent 2,889,276 Patented June 2,. 195-9 VAPOR SPACECORROSION INHIBITOR Jack P. Barrett and Loyd W. Jones, Tulsa, Okla,assignors to Pan American Petroleum Corporation, a corporation ofDelaware No Drawing. Application March 30, 1955 Serial No. 498,114

13 Claims. (Cl. 252-855) This invention relates to inhibiting corrosionof ferrous metals exposed to vapors containing hydrogen sulfide andwater vapor, and metals exposed both to vapors and liquids. Moreparticularly it relates to inhibiting corrosion of oil well casing andtubing in zones exposed to corrosive vapors as well as zones exposed tocorrosive liquids.

This is a continuation-in-part of our co-pending United Statesapplication S.N. 362,686, filed June 18, 1953, now abandoned. The parentapplication teaches the use of certain water-soluble aliphatic amines toinhibit corrosion of metals exposed to vapors containing hydrogensulfide and water. Actually the corrosion which occurs is due tocondensation of water from the vapors, usually in the form of smalldroplets, on the cool metal surfaces. This condensed water dissolveshydrogen sulfide as well as other gases such as carbon dioxide. Theliquid water solution of hydrogen sulfide and other dissolved gases isthe actual corrosive agent. It will be apparent that 'an inhibitor whichis eifective to decrease the corrosion due to such water solutions whichform from the vapors will also be effective in reducing the corrosioncaused by aqueous solutions of hydrogen sulfide at the bottom of a welland inside the tubing. The ultimate problem in both cases is to acertain extent the same. Nevertheless, the corrosion of ferrous metalsexposed to corrosive vapors in the annular space between the tubing andcasing in a Well presents problems which are somewhat diiferent fromthose offered by corrosion of ferrous metals by corrosive liquids at thebottom of the well or inside the tubing. For convenience, the corrosionof ferrous metals exposed to vapors from which water droplets containinghydrogen sulfide condense will hereafter be referred to, usually, asvapor phase corrosion. The corrosion of ferrous metals exposedpredominantly to corrosive liquids such as those at the bottom of a wellwill generally be referred to as liquid phase corrosion.

The ability of the water-soluble aliphatic amines to inhibit both vaporphase and liquid phase corrosion has been explained above. Two principalproblems arise, however, when an effort is made to use such amines forboth purposes. First, the volatile amines evaporate rather quickly whenpoured into the annular space between the casing and tubing in a well.As a result, it is "diflicult to cause the desired amount of amines toreach the liquids at the bottoms of wells. The problem is particularlyserious in wells which are very deep, which have high gas velocities inthe casing or which have high bottom hole temperatures at which thevapor pressures of the amines are quite high.

Second, several liquid phase corrosion inhibitors are available whichgive even better protection than that provided by the water-solubleamines. Obviously, then, it would be desirable to use the water solubleamines to inhibit vapor space corrosion and some of the other inhibitorsfor the liquid phase corrosion. Unfortunately, many of the liquid phasecorrosion inhibitors are not '2 compatible with the water soluble aminesand may destroy their effectiveness. For example, if formaldehyde isused as a liquid phase corrosion inhibitor it will react with the aminesto form a product having very little amine vapor pressure. Theefiectiveness of the amines to inhibit vapor space corrosion is thusdestroyed. On the other hand, the water soluble amines may adverselyaliect the liquid phase corrosion inhibitor. For example, some of therosin amines used as liquid phase corrosion l0 inhibitors seem to reactwith the lighter amines, or to polymerize in their presence, to form asolid mass of unknown properties Which would be very difficult tointroduce into a well. g

A possible solution to the use of incomptaible vapor phase and liquidphase corrosion inhibitors is to add them separately to a well onalternate days or perhaps with more than a day between use of thedifierent inhibitors. Practical considerations of use in the field makesuch a procedure most undesirable. A single composition efiective forboth vapor phase and liquid phase corrosion inhibition would obviouslybe much more desirable.

Even if a compatible liquid phase corrosion inhibitor can be found thefirst problem of causing the water soluble amine to penetrate to greaterdepth in wells is still a problem. It will be apparent that the aminecan be effective as a vapor phase inhibitor only to depths which it canreach before it evaporates. The parent aplication suggests dissolvingthe amine in solvents such as water or oil to decrease the vaporpressure. It is true that oils, for example petroleum fractions such askerosene, do decrease the amine vapor pressure, but frequently not tothe desired extent. Water, on the other hand, has been found to be tooeffective in mostcases. That is, Water solutions of the light amines donot re lease such amines from solution as rapidly as desired for manyapplications, particularly in the presence of large amounts of hydrogensulfide. A vapor pressure depressant having an efiect intermediatebetween that of oil and water is apparently needed.

With the above problems in mind an object of this invention is toprovide a composition for inhibiting corrosion of ferrous metals exposedto vapors containing water and hydrogen sulfide. An additional object isto provide a composition capable ofinhibiting both vapor phase andliquid phase corrosion by hydrogen sulfide. A more specific object is toprovide an improved inhibitor composition for decreasing the hydrogensulfide corrosion of ferrous metal surfaces exposed to corrosive vaporsin the annular space between the tubing and casing in a well and alsocapable of reducing the corrosion of ferrous metal surfaces exposed tocorrosive liquids in the bottom of the well and inside the tubing. Anadditional object is to provide improved means for causing volatilewater-soluble amines to penetrate to a greater depth in the annularspace of a well before evaporating and to evaporate more slowly to giveextended periods of treating from batch injection. I

As previously mentioned, the water-soluble aliphatic amines alone or insuitable solvents are effective inhibitors for both vapor phase andliquid phase corrosion and must be considered to be one means foraccomplishing our objects.

A greatly improved oil-soluble composition is provided by combining thewater-soluble aliphatic amines with certain higher molecular weightamines and fatty acids. The water-soluble amine may, for example, bediethylamine. The higher molecular weight amine may be octadecyl amine.The fatty acid may be the mixed acids derived from a normally liquidfraction of petroleum by liquid phase partial oxidation of the latter.

An even more highly desirable composition which is both oil-soluble andwater-dispersible can be prepared by adding certain dispersing agents,preferably in the presence of a mutual solvent and an oil, to thecombination of water soluble amine, higher molecular weight amineandfatty acid. This composition is unique in being oil-soluble,,water-dispersible and in inhibiting both vapor phase and liquid phasecorrosion.

Limitations exist on all the constituents of these compositions. Theselimitswill be outlined below in more detail. In the discussionshereinafter the water soluble aliphatic amines will be referred to aslight amines for purposes of convenience and brevity. The highermolecular weight amines will be referred to as heavy amines for the samereasons. These terms together with the other general terms fatty acids,dispersing agents," mutual solvents and oils are to be interpreted asused hereinafter to mean these general classes as limited bythefollowing more detailed descriptions.

LIGHT AMINES Certain limitations must be observed in selecting the lightamine. It must, for example, be volatile to insure adequate evaporationand diffusion to the surface to be protected. Thus, they may be termedlow-boiling amines. Amines having a maximum of about six carbon atomsper molecule should be used. All aliphatic monoamines tested containingfrom one to six carbon atoms have been found to be operable if they alsomeet the other requirements set "forth herein. O'ne requirement is thatthe amine should be non-cyclic. While many cyclic amines give highpercentage inhibition, that is, the rate of loss of metal is greatlyreduced, in general the corrosion which does occur is localized in asmall percent of the total area exposed, often as little as one percent.vicious type of local attack occurs which quickly penetrates ferrousmetals at small spots while most of the metal surface remainsuncorroded. The term aliphatic, as employed herein, includes onlyopen-chain compounds and is intended to exclude cyclic compounds such asthe cyclo-aliphatics. The primary and secondary and tertiary symmetricalmonoamines are preferred due to their high degree of effectiveness andtheir ready availability in large quantities at low cost. It will beunderstood that when the term light amine is employed hereinafter, theterm can indicate a single amine falling within the described limits, ora mixture of suitable amines.

HEAVY AMINES The heavy or high-boiling amine should contain at leastabout carbon atoms per molecule. This not only insures againstevaporation before the amine reaches the liquid phase in a well but alsoprovides protection against acombination of oxygen and hydrogen sulfidecorrosion which is not provided by acid complexes of lighter amines. Anupper limit of about twenty carbon atoms er molecular should be observedbecause of the difliculty of dissolving in oil amines of highermolecular weight. Cyclic amines such as cyclohexyl amines havingaliphatic side chains such as an octyl radical may be used. Hefer'ocyclic amines such as 2 heptadecyl imidazoline may also be, employed. Thestraight chain aliphatic amines such as octadecylamine are preferred,however, since they provide somewhat superior corrosion inhibition. Theexplanation may be that they pack together more closely on metalsurfaces to provide more corrosion-resistant films. A class of amineswhich has been found to be particularly superior to others consists ofpolyamines having two. or more amino groups. located at one end of. atleast one long hydrocarbon chain. The preferred polyarnine is obtainableunder the trademark Duomeen Tj. Other suitable fatty polyamines areobtainable under the trademarks Duom een-S and Duomeen- C. In DuomeemTthe long hydrocarbon chain is derived from ta llow acids, and hence,most of these chains are As a result, a

saturated. In Duomeen-S, on the other hand, most of the hydrocarbonchains are unsaturated since they are derived from soy bean oil acids.With Duomeen-C, the acids are derived from coconut oil and constitute amixture of saturated and unsaturated acids. Most of the hydrocarbonchains in Duomeen-T and Duomeen-S contain from 16 to 18 carbon atoms.Since coconut oil is made up of acids having a wide range of molecularweights, the resulting amines have a correspondingly varied range ofchain lengths, for example from about 8 to 18 carbon atoms. Ahydrocarbon radical of at least 10 carbon atoms should be present. Suchradicals insure the formation of a film of suflicient thickness on themetal to resist penetration even by combinations of corrosive materialssuch as oxygen and hydrogen sulfide. The straight chain aliphatichydrocarbon radicals are very much preferred to insure closer packing ofthe molecules forming the film. However, other hydrocarbon radicalshaving at least about 10 carbon atoms are also effective to a smallerdegree.

The polar portion of the amine should preferably contain at least twoamino groups separated by from 2 to 4 carbon atoms. This portion may beheterocyclic in nature but preferably should be aliphatic since thesalts of the non cyclic aliphatic polyamines have surprisingly superiorcorrosion inhibiting abilities compared to salts of the cyclicpolyamines.

So far as we have been able to determine, the aliphatic polyaminespreferred in our invention may best be represented by the formula:RNXRNHY. In this formula R is a hydrocarbon radical, preferablyaliphatic, containing from about 10 to 20 carbon atoms, N is a nitrogenatom, X is a radical selected from the group consist-- ing of R, H andRNI-IY, R isa hydrocarbon radical containing from 2 to 4 carbon atoms, His a, hydrogen atom and Y is a radical selected from the groupconsisting of H and R. The Duomeens are members of this class, havingthe simplified formula: RNHR'NH The preferred amine is Duomeen-T havingthe formula! As previously noted, R" in this formula is a mixture ofaliphatic hydrocarbon radicals most of which contain from about 16 to 18carbon atoms.

FATTY ACIDS The fatty acid should contain at least five, and preferablyat least six carbon atoms per molecule. The heavy amine complexes ofacids containing only five or six carbon atoms give some protection butfor best results the acid should contain about 10,01 more carbon atomsper molecule. Acids, containing less, than five or six carbon atomsapparently fail due to high water solubilities. As in the case, of. theheavy amines, solubility considerations set an upper limit of about 20on the number of carbon atoms in the acid molecule. The acid may containaromatic, cyclic, ether, ester or hydroxyl groups n y e ra hed un atrate We Prefer to use, however, straight chain saturated unsubstitutedacids to insure close spacing of the molecules in the protective film.Examples of suitable acids include stearic, palmitic, oleic, lauric, andthe like. obtained from vegetable and animal oils and fats. Mixtures ofthese acids m y be d or u es o ands such as those Produced in theformation of hydrocarbons by the reduction of carbon. monoxide byhydrogen over a suitable catalyst. Individual members of these acidmixtures may, of course, be isolated and used alone if, desired, butsome of the mixtures are often. preferable to avoid emulsion and gelformation difliculties, incurred when some of the purer forms ofindividualacids oracidmixtures, areused. A mixture of acids which ispreferred because the amine complexes do not, tend to form, emulsions orgels is a mixture produced from normally liquid fractions of petroleumsuch ,as kerosene by liquid phase partial oxidation in a process such asthat described in U.S. Patent 1,690,- 76 9, Burwell. Theacids may bepurified but we have found that the impurities such as alcohols,ketones, esters and the like appear toexert desirable demulsifying anddegelling action and for that reason should be retained. These acids canbe obtained under the trademark Alox 425.

Another suitable class of fatty acids consists of certain carboxylicresidues from the treatment of vegetable oils, animal oils, or acidsderived from such oils. Amine salts of acids in such residues have avery desirable decreased emulsion-forming tendency as well as increasedwater dispersibility. I [The preferred acid residue is that produced bydistilling, at about 270 C. under about 4 mm. of mercury pressure, the-by-product acids obtained in the preparation of sebacic acid by fusingcastor oil with alkali. Production of this residue is described in moredetail in U.S. Patent 2,267,269, Cheetham et al.

In the manufacture of sebacic acid from castor oil, the oil is heatedwith a caustic alkali. This splits the oil, forming octanol-2, methylhexyl ketone, the alkali salt of sebacic acid, and the alkali salts ofvarious other long-chained acids. The alcohol and ketone are readilyremoved from the reaction mixture by distillation. The alkali saltswhich remain may then be dissolved in water, and, upon slightacidification of the resulting solution, an oily layer separates. At apH of about 6, the aqueous phase contains the alkali salt of sebacicacid, while the oily layer contains various other acids from thereaction. The term by-product acids is generally applied to the mixtureof acids forming the oily layer.

These by-product acids may then be separated into two parts. After theseacids have been washed with a dilute mineral acid, such as sulfuric orhydrochloric, they may be washed with water and dried. They may then bedistilled 'under reduced pressure. Fatty acids which are primarilymonobasic carboxylic acids may be taken off at 100 C. to 270 C. atpressures as low at 4 mm. This treatment leaves a residue which is amixture of fatty acids, apparently primarily polybasic in character. Itis this residuewhich we prefer to employ in forming corrosion inhibitorswith amine salts. The residue is commercially available under thetrademark VR-l.

Other carboxylic acid residues are known which contain highly oxidizedfatty acids at least some of which are polybasic in nature. Most ofthese residues also contain alcohols, esters, and other oxygenatedhydrocarbon materials. They also generally contain a mixture of acidshaving a range of molecular weights. So far as is known these other acidresidues also produce amine salts having at least some decreasedemulsion-forming tendencies, improved water dispersibility and increasedcorrosion inhibiting ability. Examples of such acid residues are thoseproduced by the propane extraction of animal and vegetable fats, oilsand fatty acids. The process is well described and illustrated inIndustrial and Engineering Chemistry, February 1949, page 280. One suchacid residue can be obtained under the trademark Ebony Fat. This is theresidue remaining from propane extraction of fats mostly of animalorigin. Anot her specific acid residue is obtainable under the trademarkTallene. This is a residue from propane extraction of tall oil. Othersare mentioned in the Industrial and Engineering Chemistry article andstill others will occur to those skilled in the art.

The term carboxylic acid residue is intended herein to include allresidues from the treatment of animal or vegetable fats, oils or fattyacids derived from them, in which the residues contain highly oxidizedpolybasic acids containing at least about 12 carbon atoms per acidradical. The term highly oxidized is intended to indicate that the acidmolecule contains more oxygen than that present in the acid radical.

D SP S N AGENTS,

Operable dispersing agentsbelong to the class of watersoluble nonionicester-free ethers of an alcohol and a polyglycol. All members of eventhis limited family are not operable, however. The alcohol portionshould contain at least 12 carbon atoms if it is to provide suflicientoil solubility in this portion of the molecule to form the mosteifective dispersing agents. The alcohol preferably should contain nomore than about twenty carbon atoms since a larger number results indecreased oil solubility. The alcohol may be either of two principaltypes. One type consists of the straight chain aliphatic alcohols suchas lauryl and oleyl alcohol. The second type consists .of alkylatedphenols such as nonyl phenol, dinonyl phenol, octyl naphthol or thelike. .Whether the straight-chain aliphatic alcohols or alkylatedphenolsare employed,'the polyglycol portion of the dispersingagentshould contain between about 20 and about 40 oxyethylene groups forbest results. The two types of water-soluble nonionic ester-free ethersmay be conveniently described as consisting of materials having theformula HOW. In this formula H is a hydrocarbon. radical containing fromabout 12 to 20 carbon atoms, and W is a polyglycol radical containingfrom about 20 to about 40 oxyethylene groups. Preferably the dispersingagent should have the formula H'OW in which H is an'alkylated aromatichydrocarbon radical containing from about 12 to 20 carbon atoms and isattached to the oxygen linkage through the aromatic group.

The preferred dispersing agent is prepared by oxyethylating nonyl phenolbottoms; the residue remaining upon distillation of crude nonyl phenol.This material. is believed to be principally dinonyl phenol, but itcontains considerable quantities of other phenols as well as some inertmaterials. Due to the uncertain'composition it is difficult to specify anumber of oxyethylene groups per molecule of alkylated phenol. It hasbeen found that nonyl phenol bottoms reacted with from 2 to 4 timestheir weight of ethylene oxide. form operable dispersing agents. Theoptimum weight ratio ofv nonyl phenol bottoms to ethylene oxide is about1:3.

OILS

MUTUAL SOLVENTS The real problem in selecting a mutual solvent is tofind one which is a solvent for both the oil and the dispersing agent.It has been found, however, that a simpler rule to follow is to select amutual solvent for oil and water. The dispersing agent, being highlywater soluble, is also soluble in these mutual solvents for water andoil. Preferably, the mutual solvent should be miscible in allproportions, or nearly so, with both oil and water. Suitable mutualsolvents include materials such as ethers, ketones, esters and alcohols.As specific examples of the aforesaid classes of mutual solvents, theremay be mentioned acetone, methyl acetate, p-dioxane, the2-alkoxyethanols sold under the trademark Cellosolves and the lowermolecular weight alcohols such as methanol, ethanol and isopropylalcohol, said alcohols representing the preferred class of mutualsolvents which may be employed in carrying out my invention. In thisconnection, l-butanol has been successfully employed but is notsufiiciently water soluble to produce dispersions as stable as thoseformed by use of the alcohols having three or less carbon atoms permolecule. The mutual solvent performs several functions. First, it aidsin form- I now be ing a homogeneous mixture of the. water solubledispersing agent, the oil andthe oily inhibitor. Second, it aids in thedispersion of the inhibitor into the watercontacu ing the surface to beprotected. Third, the mutual solvent reduces the viscosity, gel strengthand pour point of the corrosion inhibiting composition, thusfacilitating han -dling of this composition. Methanol is a preferredmutual solvent which is easily obtained in almost anhydrous condition.

Threeprincipal compositions can be prepared employing the describedingredients. In order of increasing complexities they areas follows:First, the light amine alone or in a solvent such as oil or water may beused as a.

SIMPLE INHIBITING: COMPOSITION The simplest inhibiting composition isthelight amine or a solution of this amine in a solvent such as oil orwater. If this simplest composition is used the concentration of theamine in liquid water condensing onmetal surfaces or otherwise incontact with metal should be I from about SOto'about 500 p. p. m.. Toestablish such concentrations in water condensing in pipelines, it issug- I gested that as much as about one or two pounds of the amine(about one quart) should beintroduced into the line per million cubicfeet of gas; measured at pipeline conditions. For less severe corrosiveconditions as little as the suggested amount may be used. The amine maybe added continuously or intermittently in liquid or vapor form eitherundiluted or diluted by solvents such as water or oil. -If water drainsare set in the line added in the form of liquid or vapor, diluted orunopen top containers such asone -01: moreshallow pans disposed in thevapor space ofthe tank.

detail together with their at low spots, the concentrationofamine in thewater can be measured. The amount of amine added to gas in the line canthen be regulated to give the desired concentration in the condensedwater. If water drains are not available the gas itself can be analyzed.A suggested analytical method consists of the following steps. First,the gas is forced through a fritted glass bubble tube and into about 20ml. of water. After 15 to 20 minutes of bubbling, the bubble tube isremoved from the water and about 5 ml. of glacial acetic acid and 5 ml.of a bromphenol blue solution are mixed in. The resulting solution isthen shaken vigorously with about 20 ml. of chloroform. A yellow colorin the lower chloroform layer indicates the presence of amine in thegas. This simple test is sensitive to as little as about 0.1 or 0.2 mg.of amine per cubic ft. of gas. We have found that fair inhibition ofcorrosion by condensed water in the presence of hydrogen sulfide occurswhen even less than this concentration of amine is present in the gas.

If the amine is who used in tanks the desired concentration can usuallybe established in water droplets condensing on the underneath surface ofthe roof or on the inner walls of the tank by introducing into thevapors about one or two pounds of amine daily per million cubic feet ofvapor space.

This may be increased to as much as about 10 pounds per million cubicfeet of vapor space for extreme conditions of active use or may be aslow as A pound or less per million cubic feet per day for tanks employedin static storage. It is best to start with larger quantities andgradually decrease the quantity of amine added until the presence of theamine can just barely be detected by the method suggested above. Sincethe period of the cycle of heating and coolingis normally 24 hours, theinhibitor should be added daily to the tank. It may be The methodofapplying the invention to wells depends to some extent on whether gasis-fiowing up. the annular space between the casing and tubing. If gasis flowing it may be desirable-to introduce the amine through a macaronistring withan openend at orslightly below the lowest level at whichcorrosion is occurring. If introduced by such means, the amine may beliquid or vapor and may be diluted or undiluted. Theintroduction may beintermittent or continuous. The preferred means of introducing-theamineinto a well, whether gas is flowing or not, is to pour into theannular space of the well a solution of the amine in a relativelynon-volatile solvent such as oil, water, alcohol, or the like. Thesolution may contain from about 1 or. 2 percent up to as much as 50percent of the. amine. A convenient concentration is about-25 percent..In this connection, all percentages relating to solutionsof the lightamine are, in percent by volume. The lower limit of 1 or 2 percent isimposed to insure an appreciable vapor pressure of the amine over thesolution. The upper limit is imposed to,

obtain the eifects of dilution, which include extending the period oftreatment by decreasing the rate of evaporation of the amine andincreasing the depth to which the amine flows down. the well beforeevaporating.

' The concentration delivered to the well usually is not theconcentrationwhichflows down the annular space.

This is because the inhibitor is gener'ally'added to the. annular spacethrough alubricator to flush the inhibitor into thewell anddownthecasing- The amount of amine employed inwellswhere gas is-fiowing.through the annular space should usually be considerably morethan amounts used .in pipelines. Larger amounts are required due to thegreater water condensation rates and higher hydrogen sulfideconcentration in wells. As much as 5 or 10, pounds of amine per millioncubic feet of gas at well pressure should. be i introduced unlessexperience indicates smaller amounts to be suitable. Generally, about 1or 2 pounds of amine per million cubic feet of gas are more thansufficient. It will be noted that the solvents used with mostcompositions added to wells will reducethe vapor pressure of the amineto below that normally present in a pipeline, where the use of solventsis not so advantageous. However, the reduced vapor pressure is somewhatcompensated for by the extended time of treatment due to the action ofthe solvent. Also, in most wells the rate of flow of gas is much slowerthan in pipelines. Thus, much longer periods of exposure of the metalsurface to gases containing amines are afforded. If the rate of fiow ofgas is slow, introduction of about /2 pint of amine dissolved in agallon or more of oil, if repeated once a day, will usually be much morethan adequate. If the casing is shut in, as little as 1 pint of amineper week may be sufiicient. If the gas flow is fairly rapid, dailytreatment with as much as 3 or 4 quarts of amine dissolved in about 10or more gallons of oil may be advisable, in extreme cases. Dailyaddition of the inhibitor is recommended but in many cases, such aswhere little flow of gas is present, the amine, or preferably itssolution, may be added only once a week or at even less frequentintervals. The quantity of amine added over a given period of timeshould remain about the same, regardless of the frequency of addition.That is, the size of batch added once a week, for example, should beabout seven times the size added once a day.

Preferably, treatment should begin with heavy rates of use as high as 50times as great as the expected final rate. The initial rate is normally10 to 20 times the expected final steady rate. These large volumes atthe beginning serve to build up the concentration of light amine in thevapors. This, in turn, tends to establish quickly an equilibriumconcentration in water condensed on metal surfaces. The treatment volumeand frequency can then be decreased slowly until the desiredconcentration of amine can be detected in the gas at all times or at asuitable time after the inhibitor has been introduced. For example, ifinhibitor is added weekly, the amine should be detectable for at least24 to 48 hours after the treatment, bythe test suggested above, ifadequate protection of exposed metals is to be achieved.

OIL-SOLUBLE COMBINATION It has been found that the water-soluble aminesare perfectly compatible with the salts of the higher molecular Weightamines and fatty acids. These materials can be combined to form anoil-so1uble inhibitor combination effective for both vapor phase andliquid phase corrosion. The salt of the higher amine and fatty acid is avery loosely bound material. The substance is most commonly referred toas a complex to distinguish it from the true salts. Hereinafter the termcomplex will be employed with reference to the reaction product of theheavy amine and fatty acid. The light amine might be expected todisplace the heavy amines from this complex with the fatty acids. Thisreaction apparently proceeds to a considerable extent since the vaporpressure of the light amine is reduced by the presence of the heavyamine com plex with the fatty acids. For example, the vapor pressure ofdiethylamine over its solution in kerosene was found to be twice asgreat as the vapor pressure ofvthe same concentration of amine inkerosene containing the complex of Duomeen-T and Alox 425. Thetemperature of the solution containing the complex could be raised morethan 30 F. before the vapor pressure of the diethylamine reached thesame value as that over the solution in kerosene in the absence of thecomplex. It will be apparent, therefore, that the presence of thecomplex in oil solutions of light amines will have several verydesirable effects. First, it will cause the light amine to reach greaterdepths of Wells before evaporating from solutions. This is particularlytrue of wells having elevated bottomhole temperatures. Second, theslower rate of evaporation will mean that a batch of solution willintroduce the volatile amine into a gas stream over a longer period oftime.

The corrosion inhibiting ability of the complex is known to depend onthe presence of both the heavy amine and fatty acid. Therefore, therewas some concern regarding the effects of the reaction of the lightamine with the fatty acid. As reported in more detail hereinafter, testshave shown, surprisingly, that in spite of this reaction, and in spiteof the lower inhibiting ability of the light amines, up to about half ofthe higher amine complex with fatty acids can be replaced by the lightamine with little if any loss in inhibiting ability. In fact, some testsseem to indicate a slightly improved effectiveness due to the presenceof the light amine.

The description to this point has been directed to hydrogen sulfidecorrosion. It has also been discovered that the combination ofinhibitors is effective in decreasing the corrosion of ferrous metals byoxygen and by combinations of oxygen and hydrogen sulfide in thepresence of water whether the metal is exposed to vapors or liquids.

The principal application of the oil-soluble combination of inhibitorsis to oil wells. In this application little of the light amine may reachthe liquids in the bottom of the well. It is advisable, therefore, toemploy a ratio of heavy amine to fatty :acids which is most effective inthe absence of the light amine. Preferably, this ratio should be suchthat one carboxylic acid radical is provided for each amino nitrogenatom whether monoor poly-amines or monoor poly-carboxylic acids are employed, and whether the amine is primary, secondary or tertiary. Ifdesired, however, either the amine or the acid may be employed in anexcess up to about 100 per- 10 cent over that necessary to react withthe other. Particularly if it is desired to hold some of the light aminetightly to insure penetration to greater depths in higher temperaturewells against an upward flowof gas, it will be advisable to provide anexcess of fatty acid with which some of the light amine can react atleast temporarily.

The ratio of light amine to the complex of heavy amine and fatty acidcanvary within fairly wide limits while still retaining the advantagesof the combination. If an effective amount of the light amine is to bereleased in the vapor space'the combination should contain at leastabout 10 percent by weight of the light amine. This is also about aslittle as can be employed to decrease effectively the viscosity and pourpoint of the complex by the dilution and solvent action of the lightamine. Not more than about percent by weight of the light amine shouldbe employed if the complex is to be present in sufficient amount to behighly effective. In addition, the vapor. pressure reducing effects ofthe complex on the light amine become rather small if less than about 20percent of the combination consists of the complex, a suitable solvent,or both.

- The preferred ratio of complex to light amine is about two to onesincethe average well requires about twice as much as the complex to treatthe liquid phase as it requires of the light amine to treat the vaporphase.

The light amine serves as a diluent for the complex and the complex actsto depress the vapor pressure of the light amine. It is generallydesirable, however, to employ a solvent or diluent such as kerosene toadjust the physical properties of the combination and to depress furtherthe vapor pressure of the light amines If. the diluent is to haveappreciable effect it should amount to at least about 10 percent byweight of the solution. An upper limit of about 80 percent andpreferably not over 70 percent isimposed by the economic undesirabilityof handling a large amount of diluent containing little activeinhibitor. In addition, it has been found that the salt of the lightamine and heavy acid tends to separate from solution when the quantityof kerosene exceeds about 70 percent. .A very desirable oil-solublecombination consists of about 40 percent by weight of a diluent such askerosene, about 40 percent of a complex of an aliphatic amine such asDuomeen-T anda fatty acid such as Alox 425 and about 20 percent of alight amine such as diethylamine. Diluents other than kerosene can, ofcourse, be used with advantage. These may include, for example, alcoholssuch as methanol or isopropanol, ethers such as dioxane or dipropylether, esters such as ethyl acetate or ketones such as acetone. Somediluents such as carbon tetrachloride, carbon bisulfide, benzene, or thelike may be employed to enhance the ability of the combination toprevent deposition of paraflin or to remove parafi'in already depositedin the exposed formation or in the casing or tubing.

. Use of the oil soluble combination in wells to inhibit corrosion anddeposition of paraffin have been mentioned. In addition, the combinationmay be used in wells for other purposes such as to reduce emulsionforming tendencies in some wells, to clear water from water blockformations penetrated by the well, and to deposit lubricating films ofthe heavy amine and fatty acid to decrease rod wear. Other applicationswill occur to those skilled in the art.

While the oil soluble combination is applicable as :a corrosioninhibitor principally to wells, it is also applicable to pipelines,tanks, and refinery equipment under many conditions. For example, it hasbeen found desirable to use film-forming inhibitors such as a complex.

of higher amines and fatty acids in fractionating columns, heatexchangers, "condensers, and the like. Gen- 11 inhibitors for surfacesexposed 'to both the liquid and vapor phases but the light amine alsoacts as the desired alkaline material.

Amounts of the oil soluble combination employed in a given length oftime will vary somewhat with conditions. For most Wells a convenienttreating scheme is to add about two gallons per week of the preferredoil soluble combination. The entire volume may be added once a week orit may be added daily at a rate of about one quart per day. For wellshaving low production and mild corrosive conditions the treating ratemay be reduced to as little as a quart a week, the treating frequenciespossibly being reduced to once a month, so that about a gallon ofinhibitor is introduced in a single batch every month. For severecorrosive conditions in wells producing large volumes of fluids the ratemay be increased to as much as 20 to 30 quarts per day. In extreme caseseven more may be added.

Preferably, treatment should begin with heavy rates of use as high as 50times as great as the expected final rate. The initial rate is normallyto 20 times the expected final steady rate. This high rate at thebeginning serves to build up the concentration of light amine in thevapor space and to form a good film of the heavy amine and fatty acid onsurfaces exposed to liquids. The initial high rate may be continued foras much as several months but usually is employed for a week or two. Theinitial high rate of treatment is sometimes followed by treatments at anintermediate rate for approximately the same length of time before thefinal low steady rate is begun.

The inhibitor is normally added to a well by introducing it into thespace between the casing and tubing. The well production is thenfrequently circulated into this space to wash the inhibitor down thecasing with as much as several barrels of crude oil and brine. To avoidwashing too much of the light amine down the Well, the flush should belimited to 20 or 30 gallons. If a packer is employed in the bottom of aWell between the tubing and casing the inhibitor may be introduced intothe tubing and allowed to fall down the tubing to the bottom of thewell. It will frequently be necessary to unseat the pump and force theinhibitor down the tubing by pumping oil down after it. The inhibitormay also be introduced into the equipment to be protected by spraying itinto the vapor space. When using this technique the light amine acts insome cases as a volatile dispersant to provide a much more finelydivided spray of the liquid portions of the inhibitor composition. Thisspray technique is particularly valuable in applying the inhibitor tothe vapor spaces of tanks, to pipelines, and to refinery equipment.

The inhibitor may also housed in stick form with a suitable binder or itmay be introduced in soluble or fusible capsules such as gelatincapsules. It may also be introduced at the bottom of a well, for examplefrom a container with an orifice to regulate the rate of escape of theinhibitor.

WATER DISPERSIBLE FORM In general, the water-dispersible form ofinhibitor is prepared from the oil-soluble composition by use of themeans disclosed in more detail and claimed broadly in U.S. patentapplication 335,161, filed by Loyd W. Jones on February 4, 1953. It willbe apparent, however, that the highly polar light amine will havecertain ionic and solvent effects which must be taken into account inpreparing a water-dispersible form of the combination of the light amineand complex. In 335,1'61, Jones, five ingredients are suggested, fourbeing essential and one being optional. Essential ingredients includethe oil-soluble inhibitor, a dispersing agent, an oil and a mutualsolvent for the inhibitor and dispersing agent. The optional ingredientis water. We have found that diethylarnine or its substitute performs,to a certain extent, the functions of the oil and mutual solvent. Thus,the Water-dispersible Percent by weight Light amine 10 to Heavy aminecomplex of fatty acid 10 to 75 Dispersing agent 5 to 30 Oil O to 75Mutual solvent 0 to 10 Water 0 to 10 A preferred composition has thefollowing formula:

Percent by weight Diethyl amine l8 Neutral complex of Duomeen-T and Alox425 36 Nonyl phenol bottoms reacted with 3 times the weight of ethyleneoxide l0 Kerosene 31 Methyl alcohol 2 Water 3 The advantages of usingthe light amine with the complex of heavy amine and fatty acid are muchthe same in the water dispersible form as in the oil soluble form. Thatis, the complex controls the vapor pressure and evaporation rate of thelight amine while the amine exerts a desirable solvent action on thecomplex to improve its physical characteristics such as viscosity andpour point. The reduction in pour point is particularly valuable, theadditional solvent action of the amine serving to reduce the pour pointto a temperature below zero degree Fahrenheit.

One precaution should be noted when using the waterdispersiblecombination in wells. This concerns mixing the water dispersible formwith water at the well head or flushing the water dispersible form downthe well with water. When a water solution of the light amine contactsgases containing hydrogen sulfide the hydrogen sulfide is absorbed intothe water and reacts with the amine to form the sulfide salt. The saltis in equilibrium with its hydrolysis products, the free amine and thehydrogen sulfide. Therefore, there is a small vapor pressure of amineover a water solution of the sulfide salt of the amine. However, thevapor pressure of amine may be lower than desired for well treating.

It has been found that when a Water solution of the light amine isintroduced into a well the diffusion of hydrogen sulfide into the water,Where it reacts with the amine, occurs at such a slow rate that theamine evaporates into the vapor space and establishes the desiredconcentration there before a serious degree of reaction with hydrogensulfide takes place. Nevertheless, it is advisable in introducing any ofthe compositions containing the light amine into a well to use as littlewater as possible. The principal problem occurs, of course, when thewater dispersible form of combination inhibitor is used in a Wellproducing mostly water. When the in hibitor is flushed down the well byreturning well production into the casing only a limited amount of flushshould be employed to avoid excessive dilution of the inhibitor and toafford as little water surface as possible into which hydrogen sulfidecan difiuse.

Our invention will be better understood from consideration of thefollowing examples:

Example I To determine the effectiveness of various volatile were made.

tested were added to one liter Florence flasks each con taining 50 ml.of kerosene. The flasks were filled with deaerated water containing 5percent sodium chloride, and known concentrations of hydrogen sulfide.Tared mild steel test panels, 1 inch by 1 inch by inch, suspended onglass hooks were then lowered into the water phases in the flasks. Aftersealing, the flasks were allowed to stand quiescent for seven days at aroom temperature of about 80 F. The panels were then removed from theflasks, dipped in dilute inhibited hydrochloric acid solution, rubbedlightly to remove adhering scale, if any, rinsed in distilled water,dried and weighed. They were also visually examined to determine iflocalized corrosion had occurred. The results are presented in Table I.The amount of amine in every case was 200 parts per million by volume oftotal liquids.

TABLE I Loss of metal, mg. Percent Amine P.p.rn. Inhibi- Remarks H 8tion Control Inhibited Methyl; 600 24. 8 3. 8 84 Uniform protection.Dimetliyl 600 27. O 6. 6 76 Nolocalattack. Trimethyl 600 27. G. 7 75 Do.Ethyl 600 27.0 4. 7 83 Do. Diethyl 850 30. 3. 6 88 Uniform protection.Triethyl 600 24. 8 2. 3 91 Nolocalattack. Propyl.. 600 24. 8 4. 2 84 Do.Dipropyl--- 600 24. 8 3. 4 86 Do. Isopropyl 600 27. 0 9. 0 67 D0.DiisopropyL. 600 27. 0 5. 6 79 Do. l-B utyl 850 30. 5 9. 8 68 Uniformetching. Methyl, n-propy1 600 24. 8 2. 2 91 N olocalattack. Pyrrolidine740 23. 6 4. 0 83 Slight local attack. Pyrroline 850 30. 6 8. 0 74Fitting. 4 P1peridine 850 30. 5 4. 4 86 Severe pitting Piperaziue 85030. 5 5. 2 83 Severe local attack. Ethylenaminen 850 30. 5 6. 2 80 Verysevere local attack.

It will be noted that the non-cyclic aliphatic'monoamines permitted nolocal attack, while all the cyclic amines allowed rapid corrosion invery small scattered spots (pitting) or rapid corrosion in one or moresmall areas (local attack). Several of the aliphatic non-cyclicmonoamines did not provide perfectly uniform protection over the entirearea, but the more highly corroded areas in all cases covered at leastabout 25 percent of the total metal area. Thus, the corrosion wasdistributed over a sufliciently broad area to prevent rapid penetrationof the metal. The brine in several of the tests contained sufficientoxygen to cause a slight precipitate of elementary sulfur. Since thevolatile amines tested were operable as inhibitors in these brines, itis apparent that the amines have considerable tolerance for oxygen evenin the presence of hydrogen sulfide. This is of considerable importancein applications such as tanks where some air is usually present.

Example II To determine the ability of the amines to vaporize from asolution, difiuse through vapors, and dissolve in condensed Water toinhibit corrosion by such water, the following test was conducted. Two3.5 liter battery jars, fitted with gas-tight lids, were set up withnecessary gas and liquid inlets and outlets. Round holes were cutthrough the lids and clamping screws placed to hold round 1 /8 inchdiameter mild steel test panels over the holes. The test panels werepressed down against rubber O-rings to provide gas-tight seals.

Each jar was thoroughly swept out with air-free nitrogen first and thenwith air-free nitrogen containing 400 parts per million H S by volume.Two hundred milliliters of water were placed in the jars and one was '14treated with 0.7 ml. of diethylamine. sealed.

The whole assembly was kept in a constant temperatu re box. The bottomsof the jars were gently heated so that a temperature difierentialexisted from the bottom to the top to provide vaporization andcondensation of moisture and inhibitor.

Every 24 hours the water, inhibitor, and gas in each jar were replacedwith a fresh supply. A test panel was removed from each jar'every dayfor seven days.. The panels were cleaned as described in Example l,Weighed, and visually examined. The results are presented in Table II.

The jars were then TABLE II.Panel Weight Loss, Milligrams Percent p Theresults were somewhat erratic, as would probably be expected from thenature of the test, but the inhibiting action of the amine is apparent.The panels from the jar containing diethylamine all showed uniformprotection, no evidence of localized corrosion being visible.

Example III To determine the vapor pressure of the light amineover'various liquidsyabout ml. of the liquid were placed in a 4 literjar with a sealed top through which a dropping funnel and tubes to asample bulb and to a pump were sealed. The tube from the pump dippedbelow the liquid surface in the jar. The pump intake was connected tothe vapor space in the jar through the sampling bulb. A natural gassupply was also connected to both the pump intake and outlet. Thetechnique consisted of the following steps. The water or kerosene waslplaced in the jar and about 4 or 5 cubic feet of natural gas wereallowed to flow through the jar. The sampling tube was also flushed outwith gas. The natural gas sup- }ply was closed off and the pump intaketo the sampling bulb was opened. The desired amount of diethyl amine wasdripped through the vapor space into the liquid in the jar by means ofthe dropping funnel, and the vapors of natural gas and amine werecirculated for several hours to establish equilibrium between the liquidand vapor phases. The sample bulb was next closed off and three separatebatches of water were introduced into it to dissolve the amine. Thisamine was titrated with 0.01 N sulfuric acid using methyl red indicatorand the amount of amine in the vapors was calculated. Results arepresented in Table III.

1 The light amine was diethylamine. The complex was obtained byneutralizing Alox 425 acids with Duomeen-T.

The similarity of vapor pressure of the diethylamine over 25 percentsolutions in kerosene or water is a coincidence which is obviously nottrue for 12.5 percent solutions. Apparently the depressed vapor pressureof 12.5 percent water solutions is due to a hydration effect verysimilar to that which occurs when ammonia is dissolved in water. Theunexpectedly high vapor pressure over kerosene is probably due tosolubility effects, diethylamine and kerosene apparently not beingcompletely miscible in all proportions, but nearly so. The ability ofthe complex to depress the light amine vapor pressure is apparent fromthe data. It will also be noted that the presence of the complex makespossible increasing the temperature of the solution by F. before thevapor pressure of the light amine reaches the same value it had in theabsence of the complex.

Example IV A test was run by substantially the same procedure as inExample III to determine the effects of the presence of hydrogen sulfideon the vapor pressure of diethylamine over solutions in kerosene andwater. The only difference in the procedure consisted of passing astream of natural gas containing about 12.5 percent hydrogen sulfidethrough the jar after the system had been fiushedwith natural gas andthe amine had been introduced. This gas was not circulated, but wasvented from the system through the sample bulb, carrying some amine withit. The rate of flow of gas was about /2 to 1 cubic foot per hour. Aninitial sample of. gas was taken a few minutes after introduction of thehydrogen sulfide. Other samples were taken at intervals of 2 hours. Theresults are presented in Table IV.

TABLE IV Grams of Amine per cu. ft. Vapors Liquid in Cell RemarksInitial. 2 hrs. 4 hrs. Initial. 2 hrs.

12.5% Amine and 10% Complex in Kerosene.

12.5% Amine in Vater From the data in Table IV, it will be apparent thatthe solution of diethylamine in kerosene and the complex continued torelease vapors of the light amine into the vapors over a period of atleast two hours in spite of the rather rapid flow of gases through thecell and in spite of the presence of the hydrogen sulfide. The watersolution, on the other hand, failed to release detectable amounts of theamine into the vapors after only a few minutes contact with the gasescontaining hydrogen sulfide. It should be noted in this connection thatthe lower limit of detectability of diethylamine in the procedureemployed was about 0.2 gram per cubic foot of vapors. The presence ofamine in the vapors was easily detectable initially by use of pHsensitive indicator paper.

Example V To determine the corrosion inhibiting abilities of theoil-soluble combination of a light amine and a complex of heavy amineand fatty acid, as well as the waterdispersible form, tests were carriedout by the same procedure described in Example I. The results are pre'sented in Table V. The concentration of inhibitor in every case was 100p.p.m. and the concentration of hydrogen sulfide in the water was about600 p.p.m. The light amine employed in every case was diethylamine usedin 100 percent concentration. The complex was obtained by neutralizingAlox 425 acids with Duomeen-T and was used in the 50 percentconcentration in kerosene employed in general field practice. Thewater-dispersible complex was also employed in 50 percent by volumefield strength and was made up by mixing 4 pounds of the un- 16 dilutedcomplex, 2.57 pounds of kerosene, 0.57 pound of isopropanol and 0.26pound of a dispersing agent prepared by reacting one mole of laurylalcohol with 23 mols of ethylene oxide.

From the data in Table V it will be apparent that the combinations oflight amine with the complex in either the oil-soluble orwater-dispersible form has inhibiting ability substantially equivalentto that of the complex without the light amine. That is, substitution ofthe light amine for a part of the complex does not harm the inhibitingability. This is in spite of the lower inhibiting ability of the lightamine when used alone. The inhibiting ability of the complex even seemsto be improved slightly by the light amine in the oil-soluble form ofthe combination, thus demonstrating a slight combination inhibitingeffect.

Example VI To determine further the eifects of hydrogen sulfide on thevolatility of the light amine, a test was set up as follows. The testspecimens were 6-inch nipples of l-inch steel pipe suspended in rubberstoppers through holes in the lid of a glass jar having a capacity ofabout 3 gallons. The lower ends of the nipples were sealed by rubberstoppers. Each specimen was cooled by circulating cool water (about 50F.) through a test tube inserted into the pipe. The entire testapparatus was kept in a constant temperature box at F. The relativelycold temperature of the nipples caused a heavy condensation of water onthem from water vapor in the air which, in turn, came from the waterbelow. Duplicate test jars were set up, one containing an inhibitor andone being a control test without inhibitor. The tests were carried outas follows. First, the weighed sand blasted nipples were mounted throughthe lid and the lid sealed on the jar. Then air was removed by purgingwith nitrogen. Next, one liter of water containing 5 percent sodiumchloride and 600 p.p.m. of H 5 was introduced into the control jar. inthe test jar, the water also contained 1420 p.p.m. of diethylamine.Finally, after exposure for six weeks, the nipples were removed,cleaned, reweighed and inspected. The average weight lost by the controlnipples was 135.0 milligrams. The protected nipples lost, on theaverage, only 226 milligrams. Thus, the inhibition was about 83 percentcomplete.

Oil field brines rarely contain more than 600 p.p.m. of hydrogensulfide. Therefore, it is apparent that a water solution of diethylaminecontaining as little as 1420 p.p.m. (0.142 percent) amine will releasesuflicient amine into the vapors in most wells to protect exposed metalsurfaces from corrosion by water, containing hydrogen sulfide,condensing from the vapors. The required vaporization takes place eventhough more than enough hydrogen sulfide is present in the water toreact with all the amine, assuming that two amine molecules will reactwith one hydrogen sulfide molecule. The rate of water condensation wasmuch higher than usual for most wells since the temperature difierentialwas quite large over the very short vapor distance between the liquidWater and the cool metal surface. Therefore, it can be concluded thatthe test conditions are much-more severe than would be present in mostwells.

Example 711 Additional tests were run as described in Example VI, exceptthat the concentrations of inhibitor and hydrogen sulfide were varied.These tests were run for only 24 hours and the'test nipples werevisually inspected. The results are presented in Table VI.

TABLE VI I -Parts Per Million in Treating Water Results DEA 1 H 8 100600. Failed. 200 600- D0. 400 680- D0. 800 680--. Do. 1,200 680--.Partial protection. 1,500 680..- Good protection. 2,000 600 Excellentprotection. 1,000 1,300 Failed; 2,000 Saturated (1,800 p.p I Do.

1 DEA isdiethylamine.

These data seem to indicate that under thetest conditions, theconcentration of light amine should be at least about twice as great asthat of hydrogen sulfide in the brine if good protection is to beprovided for metal surfaces exposed to condensing water vapors. Actuallythe relationship is probably much more complex and probably depends onthe mass action elfect of the hydrogen sulfide to decrease thedissociation of the amine sulfide and amine acid sulfide into theircomponent parts. The vapor pressure of the amine thus probably alsodepends on the concentration of amine sulfide present, temperature ofsolution, presence or absence of the complex of heavy .amine and fattyacid and the like.

. .E xamp le VIII. 7

Thetest described in Example VII was repeated, except that the complexof Duomeen-T and Alox 425 was added. The complex was added in thewater-dispersible form, one series of tests being made using a formulacontaining about 3.00 pounds of the neutral complex of Duomeen-T andAlox 425, about 0.75 pound of diethylamine, about 0.36 pound ofisopropanol, about 0.20 pound of the reaction product of one mole oflauryl alcohol and 23 moles of ethylene oxide, about 2.72 pounds ofkerosene, and about 0.05 pound of water. This formulacontains about 10percent diethylamine and will be referred to in Table VII as compound A.The other formula contained about 18 percent diethylamine and wasprepared by mixing 2.5 pounds of the heavy amine-acid complex, 1.3pounds of diethylamine, 2.55 pounds of kerosene and 0.8 pound of anemulsifier prepared by reacting nonylphenol bottoms with three times itsweight of ethylene oxide. This formula will be referred to in Table VIIas compound B. Thus, the diethylamine concentration of 2,000 p.p.m.reported in Table VII has associated with it twice as much of thecomplex when compound A is used as when compound B is employed. 2

TABLE VII Parts Per Million in Treating Water Results DEA 1 H18 1,000(from Compound A) 680 I Some protection. 2,000 (from Compound A) 680Fair protection. 3,000 (from Compound A 680 Good protection. 4,000 (fromCompound A 680 Excellent protection. 1,500 (from Compound B 680 Fairprotection. 2,000 (from Compound 13) 680 Good protection.

1 DEA is diethylamine.

r 18 A comparison of data in Tables VI and VII-shows that 2000 p.p.m.diethylamine in water evaporates to different degrees, depending on theamount of heavy aminefatty acid complex present. With no complex present(Table VI), enough diethylamine evaporates to give excellent protectionof metals exposed to the vapors. With an intermediate amount of complexpresent (compound v B, Table VII), less amine is present in the vapors,but still enough to provide good protection. When .a large amount ofcomplex is present, however (compound A, Table VII), only enough amineevaporates to give fair protection. Even with the larger amount ofcomplex present, however, the presence of 4000 p.p.m. of diethylamine inthe liquid water resulted in evaporation of sufficient amine to produceexcellent protection of metal surfaces exposed to the vapors. Since 4000p.p.m. is 0.4 percent, and since the Water-dispersible complex maycontain as little as 10 percent of the light amine, it will be apparentthat the complex should be diluted by only 20 to 25 times its volume ofwater when it is injected into a Well containing a high concentration ofhydrogen sulfide if the best protection of metal parts exposed to vaporsis to be obtained. For wells containing less hydrogen sulfide, thedilution can be much greater.

Example IX The data in Examples VII and VIII demonstrate the difiicultyof predicting the amount of light amines, or their combinations withheavy amine-fatty acid complexes, required in any particular case.Therefore, a series of tests was run to determine the actualconcentration of amine in the vapors in cases where good protection ofmetal surfaces occurred and also the concentration Where good protectionwas not obtained. In this series of tests, two five-gallon bottles wereconnected so gas could be circulated between them by means of a pump.Two liters of 5 percent sodium chloride brine containing known amountsof diethylamine and hydrogen sulfidewere poured into one bottle. The gaswas then recirculated for 17 hours to establish liquid-vaporequilibrium. The bottle containing only. gas wasv then disconnected, 100ml. of Water were added, and the bottle was vigorously shaken andallowed to stand one hour to absorb amine. This Water was then analyzedfor amine content by the test described above under the heading SimpleInhibiting Composition. A calibration curve was prepared on colorintensity to permit approximate quantitative analysis. The results arepresented in Table VIII.

TABLE VIII Parts Per Million in Treating Water Milligrams of DEA percubic foot of DEA HIS Gas 500 Saturated (1,800 7 None p.p.m.). 2,000Saturated None 2,000 1,250.. 17 2,000 500 1 40 2,000 (from Compound A) 2680 None 2,000 (from Compound B) 5 680 15 I Probably high because ofcondensate in test bottle. 1 Compounds A and B are the same as describedin Example VIII.

A comparison of these results with the corrosion inhibiting results inTables VI and VII shows that good or excellent protection is provided bythe presence of 10 or more milligrams of diethylamine in the vapors. Ofparticular significance is the fact that 2000 p.p.m. of diethylamine inthe presence of the complex in compound A did not produce an amount ofamine in the gas which was detectable by this test. Nevertheless, TableVII shows that sufiicient amine was present in the vapors to give fairprotection to metal surfaces exposed to the vapors.

after two days.

aaetravo f It' follows, therefore," that if a. detectable'arnount of"light amine is present in thegas'es, at "least fairprotection of metalexposed to the vapors is being provided. For good results at least about10 milligrams of amineper cubic 'tom of the'well before the'amine'can'evaporate. It'will also be apparnt'fromthe data,- however, that someflush is needed to avoid loss ofall the amine near the top of the well.See, for example, the low concentracsg.

foot of gases should be maintained. For best results, tion of-am'ine in;the gas one day after introducing 2 the concentration should exceedabout 20 milligrams gallons of the inhibitor solution without flushing.per cubic foot. Thesevalues apply, of course, only to From the abovedescription and examples, itwill'be cases 'where'the rate of watercondensation is the same or pparent that We ave accomplished the O jectsof ur higher than that present in the tests. For lower rates'of inventin- I ii r c p i have been provided water condensation,much lowerconcentrations in the awhich protect both metal surfaces exposed tocorrosive p'ors will establish and maintain corrosion-inhibitingconvapors containing hydrogen sulfide and water and metals centrationsof light amine in'the water; It'shouldalso be exposfid to liquids ntaning Water and hydrogen sulnoted that the rate of evaporation of theamine from Compatible combiflafionsof'light amines with h dilutesolutions in water is very "slow, particularly if acidic 1y fifi t vecomplexes Of heavy amin s and fatty acids materials such as hydrogensulfide and carbon dioxide a al been provided in b th ilol bl andWaterare present. Therefore, once an inhibiting concentradispersibleform in which the light amine improves the tion o f'IOO p.p.m. or moreof the amine has been esproperties of the complex'and the'complex'controls the tablished in condensed Water, it will be unnecessary to rae of apo ofthe light amine. maintain'a'continuous concentration of lightamine in the We claim: P f ja Intermittent 'additiqn mine has f fl 1.Amethodofinhibiting' corrosion of ferrousmetals to b .perfectly adequateF compensate .Shght 9. exposed to liquid water containing hydrogensulfide com- $3 f mi l also comp ensate for I prising establishing insaid water a concentration of at dllutlon of the amine concentration dueto continued conleast about 50' parts per illion by weight of a freealidensamm of Water on the metal surfaces phatic monoamine containingfrom 1 to 6 carbon atoms Example X per molecule, said monoamine beingpresent in' an amount 1 g lficient to combine with only a minor amountof the To determine the suitability of Oll solutions of light Sn camines for use in wells, solutions of diethylamine in hydrogen smfide lfy the monoamme' kerosene, containing one quart of amine per gallon of ofP PQ farms metals solution, were introduced into the annular spacebetween 329 .5 P Q W f r q a m g Sulfide the tubing and casing of apumping well in the North Pnsmg establlshmg fi coflcentratwn of a CowdenField ofTexas. The Well as producing about j bpu i i ri p by Welght of a115,000 cubic feet of gas per day from'the well annulus. h QQPP F QF fl-QIP t egroup cons stmg of The rate of injection of the inhibitorsolution and conm m Zn Pl l'l l n 9 l centrationofamine in the gas areshown in Table IX. s thyl mq x m st mPY dlprqpylamine Analysis for aminecontent of the gas Was made by q p sm q ifl y lm y mm n f bubbling ameasured amount of gas through a dilute smd'rPonoafnmebemg 235 ImamuntSuffic1entt acetic acid solution to absorb the amine and analyzingthe f wlthfmly a mmoramoum of hydrogen water solution for amine content.Flushing was acfide the fluids treatedby the monoamme' coinplished byreturning the well production for the noted 3. The method of claimZin'Which said amine is ditime tothe'well annulus. ethylamine.

TABLE IX Gallons Gas Sem- Amine Day Time Inhibitor ole Vo1., Content ofRemarks Solution Cu. Ft. at Gas, Mg./

Csg. Pres. Cu. Ft.

1 $383313: me ilfiii i tiii g. flowline valve closed. 7 9:00 a.m .133None 17 hrs. after treatment. Amine detected in liquid 2, production. I10:00 am 2 2 min. flush, csg. flowline valve closed. 4% hrs. aftertreatment. One day after treatment. No flush,

valve open. One day after treatment. 2 min. flush, csg. flowline valveclosed.

5 {9:00 am 133 7. 5 One day after. treatment; 3 10:00 a.m 2 2 min.flush, csg. fiowline valve closed. 250 20 One day after treatment. 300Trace Two days after treatment.

, gases over a period of a 'day following injection of 2 gallons of the25 percent solution of amine in kerosene; Detactabl'e traces ofaminewere present in the gas even This is in spite of'the flow of about115,000 cubic feet of gas per day out of the well through theannulus.Since amine was detected in liquids produced from the well, protectionwas being provided to the bottom of the 4000 foot well. It will beapparent that the'amount of flushing should be limited to avoid washing4. A method for inhibiting in a well corrosion of fercontaining hydrogensulfide and water vapors as well as corrosion of ferrous metals exposedto liquid water containing hydrogen sulfide in the bottom of the wellcomprising introducing into said well a free aliphatic monoamineselected from the 'group consisting of methylamine, dimethylamiue,trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,dipropylamine, isopropylamine, diisopropylamine, and 1-butylarnine, andflushing said amine down the-well with sufi'icient liquid to carry toomuch of the amine down into the liquids at the bot acorrosion-inhibiting amount of said amineto the bottom 21 ,of thewell,said monoaminebeing present in an amount sufiicient to combine with onlya minor amount ofthe hydrogen sulfide in the fluids treated by themonoamine.

5. The method of claim 4 in which said amine is diethylamine. 6. Animproved composition for inhibiting corrosion of ferrous metals exposedto water condensing from vapors containing hydrogen sulfide and watervapors, as well as corrosion of ferrous metals normally exposed toliquid water containing hydrogen sulfide comprising a combination offrom about 10 to 80 percent by weight of a free low-boiling aliphaticmonoamine containing from 1 to 6 carbon atoms per molecule and fromabout 20 to 90 percent of a salt of a high-boiling aliphatic amine and acarboxylic acid, said high-boiling amine containing at least 10 carbonatoms per molecule and said acid containing at least 6 carbon atoms permolecule, and said salt consisting of from /2 to 2 times the amount ofhigh-boiling amine necessary to neutralize said carboxylic acid.

7. The composition of claim 6 in which said low-boiling amine isselected from the group consisting of methylamine, dimethylamine,trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,dipropylamine, isopropylamine, diisopropylamine, and l-butylamine, saidhigh-boiling amine has the formula RNHR'NH wherein R is an aliphatichydrocarbon radical contain ing from about 10 to 20 carbon atoms and Ris a hydrocarbon radical containing from 2 to 4 carbon atoms, and saidcarboxylic acid is derived from a normally liquid fraction of petroleumby liquid phase partial oxidation of the latter.

8. The composition of claim 6 in which said low-boiling amine isselected from the group consisting of methylamine, dimethylamine,trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,dipropylamine, isopropylamine, diisopropylamine, and l-butylamine, saidhigh-boiling amine has the formula RNHR'NH wherein R is an aliphatichydrocarbon radical containing from about 10 to 20 carbon atoms and R isa hydrocarbon radical containing from 2 to 4 carbon atoms, and saidcarboxylic acid is the residue produced by distilling at about 270 C.under about 4 millimeters of mercury pressure the by-product acidsobtained in the preparation of sebacic acid by fusing castor oil withalkali.

9. A method for inhibiting in a well corrosion of ferrous metals exposedto water condensing from vapors containing hydrogen sulfide and watervapors as well as corrosion of ferrous metals exposed to liquid watercontaining hydrogen sulfide in the bottom of the well comprisingintroducing into said well a combination of from about 10 to 80 percentby weight of a free low-boiling aliphatic monoamine containing from 1 to6 carbon atoms per molecule and from about 20 to 90 percent of a salt ofa high-boiling aliphatic amine and a carboxylic acid, said high-boilingamine containing at least 10 carbon atoms per molecule and said acidcontaining at least 6 carbon atoms per molecule, and said saltconsisting of from V2 to 2 times the amount of high-boiling aminenecessary to neutralize said carboxylic acid.

10. A water-dispersible, oil-soluble composition for inhibitingcorrosion of ferrous metals exposed to water condensing from vaporscontaining hydrogen sulfide and water vapors, as well as corrosion offerrous metals normally exposed to liquid water containing hydrogensulfide comprising a combination of from about 10 to 30 percent byweight of a free low-boiling aliphatic monoamine, containing from 1 to 6carbon atoms per molecule, from about 10 to 75 percent of a salt of ahigh-boiling aliphatic amine and a carboxylic acid, from about to 30percent of a dispersing agent, from 0 to about 75 percent of an oil,from 0 to about percent of a mutual solvent for oil and water, and from0 to about 10 percent of water, said high-boiling amine containing atleast 10 carbon atoms per molecule and said acid containing at least 6carbon atoms per molecule and said dispersing agent being an ester-freeether having the formula HOW wherein H is a hydrocarbon radicalcontaining from about 12 to 20 carbon atoms and W is a polyglycol"radical containing from about 20 to 40 oxyethylene groups, and saidsalt consisting of from /2 to 2 times the amount of high-boilingaminenecessary to neutralize said carboxylic acid. a 7

11. The composition of claim 10 in which said lowboiling amine isselected from the group consisting of methylamine, dimethylaminetrimethylamine, ethylamine, diethylamine, triethylamine, propylamine,dipropylamine, isopropylamine, diisopropylamine, and l-butylamine, saidhigh-boiling amine has the formula RNHRNH wherein R is an aliphatichydrocarbon radical containing from about 10 to 20 carbon atoms and R isa hydrocarbon radical containing from 2 to 4 carbon atoms, and saidcarboxylic acid is derived from a normally liquid fraction of petroleumby liquid phase partial oxidation of the latter, said dispersing agentis an ester-free ether having the formula H'OW wherein H is an alkylatedaromatic hydrocarbon radical containing from about 12 to 20 carbon atomsattached to the oxygen linkage through the aromatic group, and W is apolyglycol radical containing from about 20 to 40 oxyethylene groups,said oil is a liquid petroleum fraction, and said mutual solvent is analcohol selected from the group consisting of methyl alcohol, ethylalcohol and isopropyl alcohol.

12. The composition of claim 10 in which said lowboiling amine isselected from the group consisting of methylamine, dimethylamine,trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,dipropylamine, isopropylamine, diisopropylamine, and l-butylamine, saidhigh-boiling amine has the formula RNHRNH wherein R is an aliphatichydrocarbon radical containing from about 10 to 20 carbon atoms and R isa hydrocarbon radical containing from 2 to 4 carbon atoms, saidcarboxylic acid being the residue produced by distilling at about 270 C.under about 4 millimeters of mercury pressure the by-product acidsobtained in the preparation of sebacic acid by fusing castor oil withalkali, said dispersing agent is an ester-free ether having the formulaH'OW wherein H is an alkylated aromatic hydrocarbon radical containingfrom about 12 to 20 carbon atoms attached to the oxygen linkage throughthe aromatic group, and W is a polyglycol radical containing from about20 to 40 oxyethylene groups, said oil is a liquid petroleum fraction,and said mutual solvent is an alcohol selected from the group consistingof methyl alcohol, ethyl alcohol and isopropyl alcohol.

13. A method for inhibiting in a well corrosion of ferrous metalsexposed to water condensing from vapors containing hydrogen sulfide andwater vapors as well as corrosions of ferrous metals exposed to liquidwater containing hydrogen sulfide in the bottom of the well comprisingintroducing into said well a combination of from about 10 to 30 percentby weight of a free low-boiling aliphatic monoamine containing from 1 to6 carbon atoms per molecule, from about 10 to 75 percent of a salt of ahigh-boiling aliphatic amine and a carboxylic acid, from about 5 to 30percent of a disperesing agent, from 0 to about 75 percent of an oil,from 0 to about 10 percent of a mutual solvent for oil and water, andfrom- 0 to about 10 percent of water, said high-boiling amine containingat least 10 carbon atoms per molecule and said acid containing at least6 carbon atoms per molecule and said dispersing agent is an ester-freeether having the formula HOW wherein H is a hydrocarbon radicalcontaining from about 12 to 20 carbon atoms and W is a polyglycolradical containing from about 20 to 40 oxyethylene groups, and said saltconsisting of from to 2 times the amount of high-boiling amine necessaryto neutralize said carboxylic acid.

(References on following page)

1. A METHOD OF INHIBITING CORROSION OF FERROUS METALS EXPOSED TO LIQUIDWATER CONTAINING HYDROGEN SULFIDE COMPRISING ESTABLISHING IN SAID WATERA CONCENTRATION OF AT LEAST ABOUT 50 PARTS PER MILLION BY WEIGHT OF AFREE ALIPHATIC MONOAMINE CONTAINING FROM 1 TO 6 CARBON ATOMS PERMOLECULE, SAID MONOAMINE BEING PRESENT IN AN AMOUNT SUFFICIENT TOCOMBINE WITH ONLY A MINOR AMOUNT OF THE HYDROGEN SULFIDE IN THE FLUIDSTREATED BY THE MONOAMINE.
 9. A METHOD FOR INHIBITING IN A WELL CORROSIONOF FERROUS METALS EXPOSED TO WATER CONDENSING FROM VAPORS CONTAININGHYDROGEN SULFIDE AND WATER VAPORS AS WELL AS CORROSION OF FERROUS METALSEXPOSED TO LIQUID WATER CONTAINING HYDROGEN SULFIDE IN THE BOTTOM OF THEWELL COMPRISING INTRODUCING INTO SAID WELL A COMBINATION OF FROM ABOUT10 TO 80 PERCENT BY WEIGHT OF A FREE LOW-BOILING ALIPHATIC MONOAMINECONTAINING FROM 1 TO 6 CARBON ATOMS PER MOLECULE AND FROM ABOUT 20 TO 90PERCENT OF A SALT OF A HIGH-BOILING ALIPHATIC AMINE AND A CABOXYLICACID, SAID HIGH-BOILING AMINE CONTAINING AT LEAST 10 CARBON ATOMS PERMOLECULE AND SAID ACID CONTAINING AT LEAST 6 CARBON ATOMS PER MOLECULE,AND SAID SALT CONSISTING OF FROM 1/2 TO 2 TIMES THE AMOUNT OFHIGH-BOILING AMINE NECESSARY TO-NEUTRALIZE SAID CARBOXYLIC ACID.